Magnetic stirrer and temperature regulation device



Aug. 1, 1967 MQORE ET AL 3,333,829

MAGNETIC STIRRER AND TEMPERATURE REGULATION DEVICE Filed April 21, 1966T Q22 HHHII will;

DAPRLLE 0. MOORE EDWARD L VER V4/S United States Patent M 3,333 829MAGNETIC STIRRER AND TEMPERATURE REGULATION DEVICE Darrlle D. Moore andEdward L. Ver Vais, Dubuque,

ABSTRACT OF THE DISCLOSURE A temperature regulation device, utilized incombination with a magnetic stirrer in laboratory and similarapplications. A thin, flat, rigid, non-magnetic chamber is positioned onthe surface of the magnetic stirrer base, between the stirrer base and avessel containing a stirring magnet; cooling fluid is circulated throughthe chamber to regulate the temperature of the vessel contents.

Background of the invention Magnetic stirrers have found increasing usein a variety of applications, particularly in laboratories for use intitrations, culturing, extractions, and other processes. A magneticstirrer usually includes a base having an appropriate cover or topsurface for supporting a beaker or other vessel. A magnetic driveelement, usually a permanent magnet, is positioned within the baseimmediately below the cover. The vessel containing the material to bestirred is supported on the cover of the stirrer and a small permanentmagnet or other appropriate magnetic stirring element is placed withinthe vessel, over the magnetic drive element in the base. Stirring isaccomplished by rotating the magnetic drive element, the magnetic fieldlinkage between the drive element and the stirring element causing.corresponding rotation of the stirring element and achieving thedesired agitation of the vessel contents.

Some magnetic stirrers of this general kind are provided with opaquecovers; the cover may be of nonmagnetic sheet metal or may be made ofplastic or other suitable materials. One particularly advantageouscommercial form of magnetic stirrer is that described and illustrated inUnited States Letters Patent No. 3,138,370 issued June 23, 1964 toCleophas B. Anderson and Germain B. Pins. The magnetic stirrer of thepatent is provided with a transparent cover and with one or moreelectrical lamps mounted within the base. This makes it possible toilluminate the contents of the vessel from be low, through thetransparent cover plate, a highly desirable arrangement for manylaboratory and other applications.

For many laboratory procedures where magnetic stirrers are employed, itis critically important to prevent heating of the vessel contents duringthe stirring operation. With virtually all magnetic stirring devices,however, at least some heat is generated and transmitted to the vesselcontaining the material being stirred. Basically, this heat has threesources. The primary source of the undesired heat is the drive motor forthe magnetic drive element. Unless an elaborate fan and ventilationsystem is adopted, which is usually economically impractical, asubstantial amount of the heat developed by the stirrer motor isfrequently transmitted to the Vessel in which the stirring operationtakes place.

Another principal source of heat is eddy currents in duced in the usualmetal housing for the magnetic stirrer base. The rotating magnetic fieldbetween the magnetic drive and stirring elements can produce appreciableheat due to eddy currents developed in a metal cover plate on the base.Even where a plastic or other insulator cover is used, the eddy currentsdeveloped in the re- 3,333,829 Patented Aug. 1, 1967 mainder of themetal housing for the stirrer base, by the fringe portions of themagnetic field, can be noticeable.

A third source of heat that may be of some importance is present in aself-illuminated magnetic stirrer of the kind described in the Andersonet a1. Patent No. 3,138,- 370. A substantial portion of the heatdeveloped by the lamps used for base illumination may be absorbed by thevessel.

Summary of the invention It is a primary object of the presentinvention, therefore, to provide a simple, practical and inexpensivetemperature regulation device for a magnetic stirrer of the kinddescribed hereinabove.

A further object of the invention is to afford an effective temperatureregulation device for a magnetic stirrer that nevertheless permitsillumination of a vessel containing the material being stirred directlyfrom below by means of light sources located in the magnetic stirrerbase.

Another object of the invention is to aiford a temperature regulationdevice for a magnetic stirrer that does not inherently add any heat tothat already produced by the stirrer.

A further object of the invention is to afford a simple temperatureregulation device for a magnetic stirrer that permits moderate buteffective cooling or, alternatively, moderate but effecting heating ofthe material being stirred.

An additional object of the invention is to provide a temperatureregulation device for a self-illuminated magnetic stirrer that iseliective as a light filter, in addition to its temperature regulationfunctions.

Accordingly, the present invention relates to a temperature regulationdevice for a magnetic stirrer of the kind comprising a base having acover, a magnetic drive element positioned within the base below thecover, and a magnetic stirring element positioned within a vessel thatis supported on the cover. The magnetic stirrer further includes meansfor rotating the magnetic drive element to stir the contents of thevessel by rotating the magnetic stirring element through the magneticfield linkage between the magnetic elements. The temperature regulationdevice of the invention comprises a thin, flat housing of non-magneticmaterial that is also preferably electrically non-conductive; thishousing defines a fluidtight chamber having an effective surface areaapproximating the surface area of the cover of the magnetic stirrer.This housing is positioned on the cover of the magnetic stirrerintermediate the cover and the vessel containing the material beingsitrred. The temperature regulation device further includes means,comprising inlet and outlet conduits connected to the chamber, forcirculating fluid through the chamber to regulate the contents of thevessel containing the material to be stirred. Usually, the circulatingfluid is ordinary tap water.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which, by way of illustration, show preferredembodiments of the present invention and the principles thereof and whatis now considered to be the best mode contemplated for applying theseprinciples. Other embodiments of the invention embodying the same orequivalent principles may be made as desired by those skilled in the artwithout departing from the present invention.

Description of the drawing FIG. 1 is a prespective view of a magneticstirrer and a temperature regulation device for the stirrer constructedin accordance with the present invention;

FIG. 2 is a plan view of the temperature regulation device mounted inposition of use on the magnetic stirrer;

FIG. 3 is an elevation view, partly in cross section, takenapproximately along line 33' in FIG. 2;

FIG. 4 is a transverse sectional view of the temperature regulationdevice taken approximately as indicated by line 4-4 in FIG. 2; and

FIG. 5 is a detail sectional view, drawn to an enlarged scale, takenapproximately as indicated by line 5-5 in FIG. 2.

Description of preferred embodiment FIGS. 1, 2'and 3 illustrate atemperature regulation device constructed in accordance with preferredembodiment of the present invention, mounted in position of use upon amagnetic stirrer 11. The magnetic stirrer 11 corresponds in constructionto that disclosed in Patent No. 3,138,370. It comprises a sheet metalbase 12 having a cover 13. The central portion of the cover 13constitutes a transparent plastic cover plate 14.

A magnetic drive element is positioned within the base 11 below thecoverplate 14 and located centrally with respect to the cover plate.Magnetic drive element 15 constitutes a small permanent magnet. Themagnetic drive element 15 is mounted in a diametrical groove in acoupling member 16, being held in place by an appropriate clamp 17. Thecoupling member 16 is connected, by a hub 18, to the drive shaft of asmall electrical motor (not shown), the coupling thus affording a meansfor rotating the magnetic drive element 15 about the axis of thecoupling.

In conventional use of the magnetic stirrer 11, a vessel containing thematerial to be stirred would be supported directly upon the cover plate14 of the stirrer base. In accordance with the present invention,however, this practice is not followed. Instead, the temperatureregulation device 10 is disposed upon the cover plate 14 of the magneticstirrer and a vessel 21 containing the material 22 to be stirred is inturn supported upon the temperature regulation device (see FIGS. 1 and3). A magnetic stirring element 23 that is used with and constitutes apart of magnetic stirrer 10 is positioned in vessel 21; this magneticstirring element preferably comprises a small permanent magnet and maybe provided with an inert coating to permit use of the stirrer insolutions and other materials that would otherwise attack the permanentmagnet. In use, magnetic stirring element 23 rotates in response torotation of the magnetic drive element 15, due to the magnetic fieldlinkage between these elements, and thus stirs the material 22 withinvessel 21.

Temperature regulation device 10 comprises a thin .flat housingconstructed in the form of two quite shallow dish-like housing members26 and 27. The two housing halves 26 and 27 are sealed to each otheraround their rims; the rims of the two housing members may be ccmentedto each other or a heat fusion bond may be employed if desired, assumingan appropriate material is used in fabricating the housing. Similarly,the central portions of the two housing members are sealed together. Inthis instance, an eyelet 28 is employed to provide a strong mechanicaljoint (see FIG. 4). In addition, or by way of substitution, a cementbond or fusion bond can also be used. Other appropriate means forsecuring the two housing halves together can be utilized, or othermanufacturing techniques may be employed to produce a thin-wall housing,as desired, so long as the housing defines a fluid-tight chamber 29within the housing.

The housing 26, 27 should be fabricated from a nonmagnetic material. Ifa magnetic material is employed, it detracts materially from themagnetic coupling between members 15 and 23 and thus interferes with thedesired stirring action. Furthermore, it is preferred that the housingof the temperature regulation device 10 be made of electricallynon-conductive material to avoid the generation of eddy currents in thehousing. If the housing comprises an electrical conductor, the rotatingelectrical field extending between the magnetic members 15 and 24produces eddy currents in the housing and this may lead to undesirableheating. In the preferred form of the invention, as illustrated, thehousing members 26 and 27 are constructed from a transparent plastic. 7

The fluid-tight chamber 29 within the temperature regulator housing hasan effective surface area that is generally similar to the usefulsurface area of the cover of the magnetic stirrer. In the embodiment ofthe invention as illustrated, the temperature regulating device issomewhat smaller than the cover and this is quite permissible, but thedevice should be of the same order of magnitude, with respect to surfacearea, as the stirrer cover in order to afford uniform temperatureregulation as described hereinafter.

Temperature regulation device 10 is provided with an inlet conduit ornipple 31 that connects with the interior of chamber 29. A similaroutlet conduit 32 is'also provided. Actually, conduits 31 and 32 areinterchangeable and either may be used as the inlet or outlet conduit atdifferent times. These conduits afford a means for circulating fluidthrough chamber 29.

In the construction illustrated in the drawings, a barrier 33 is locatedwithin the housing 26, 27. Barrier 33, as shown in FIGS. 2 and 4,extends from a point immediately between the inlet-outlet conduits 31and 32 to the center of the chamber 29. The use of a barrier such asmember 33 is not essential to operation of the device and may be omittedin some instances.

In use, a hose or other similar conduit extension 35 is connected to theinlet conduit 31. In the usual application, the other end of hose 35(not shown) is connected to a water tap or other suitable source offluid at a desired temperature. Similarly, a hose or like conduitextension 36 is connected to the outlet conduit 32. Hose 36 may lead toa drain or to a re-circulating pump. Where substantial temperaturereduction is required, the hoses 35 and 36 can be connected to arefrigerating apparatus to reduce the temperature of the fluid used indevice 10 well below ambient temperature.

In operation, ordinary cold tap water may be circulated through device10, introduced into the annular chamber 29 through inlet conduit 31. Thefluid is continuously exhausted from the chamber, once the chamber isfilled, through outlet conduit 32 and hose 36. In most processes, only alimited cooling effect is desired so that tap water provides sufficientcooling. If water from the cold tap is too cold and reduces thetemperature of the material 22 below the desired level, it is a simplematter to connect hose 35 to a conventional mixing faucet and to mixsome warm water with cold water to achieve the desired effect. By thesame token, if a moderate increased heating effect is desired, warm orhot water alone may be circulated through the temperature regulationdevice 10 for this purpose.

As noted above, housing members 26 and 27 are preferably fabricated froma transparent plastic material. Accordingly, where cover plate 14 (FIG.3') is transparent and where the stirrer 11 includes a light source inthe base, as disclosed in Patent No. 3,138,370, the use of asubstantially transparent cooling liquid makes it possible to illuminatethe bottom portion of vessel 21 with little or no reduction inefficiency. Thus, the temperature regulation device does not interferewith the self-illuminated magnetic stirrer operation.

In some laboratory applications, it is desirable to illuminate vessel 21with light of a particular color; more expressly, it may be desirable tofilter out a predetermined portion of light transmitted from the base ofthe magnetic stirrer to the vessel containing the material beingstirred. This can be accomplished in one of two ways. It is readilypossible to add a dye to the fluid circulating through device 10 thatwill effectively filter the light reaching the vessel 21 from the baseof the magnetic stirrer. On the other hand, the plastic housing 26, 27may be tinted in manufacture to afford a filter capable of obtaining thedesired results.

Hence, While preferred embodiments of the invention have been describedand illustrated, it is to be understood that they are capable ofvariation and modification.

We claim:

1. In combination with a magnetic stirrer of the kind comprising a basehaving a cover, a magnetic drive element positioned within said basebelow said cover, a magnetic stirring element positionable within avessel supported on said cover, and means for rotating said magneticdrive element to stir the contents of said vessel by rotating saidmagnetic stirring element through magnetic field linkage between saidmagnetic elements, a temperature regulation device comprising a thin,flat housing of non-magnetic material, defining a fluid-tight chamberhaving an eifective surface area approximating the surface area of saidcover, positionable on said cover intermediate said cover and saidvessel, and means, including inlet and outlet conduits connected to saidchamber, for circulating fluid through said chamber to regulate thetemperature of the contents of said vessel.

2. A temperature regulation device in combination with a magneticstirrer, according to claim 1, in which said housing is of electricallynon-conductive material to prevent development of substantial eddycurrents therein.

3. A temperature regulation device in combination with a magneticstirrer, according to claim 1, in which said chamber is of annularconfiguration, with said inlet and outlet conduits located closelyadjacent each other, and having a barrier extending from a point betweensaid conduits to the center of said chamber to assure flow of said fluidcompletely around said chamber.

4. A temperature regulation device in combination with a magneticstirrer, according to claim 1, in which said housing is of transparentplastic material to allow passage of light from said base through saidhousing to said vessel.

5. A temperature regulation device in combination with a magneticstirrer, according to claim 4, in which said transparent housing istinted to filter out predetermined portions of light transmitted fromsaid .base through said device to said vessel.

References Cited UNITED STATES PATENTS 2,518,758 8/1950 Cook 2591083,138,370 6/1964 Anderson 259-108 3,233,662 2/1966 Chuen l46 WALTER A.SCHEEL, Primary Examiner.

ROBERT W. JENKINS, Examiner.

1. IN COMBINATION WITH A MAGNETIC STIRRER OF THE KIND COMPRISING A BASEHAVING A COVER, A MAGNETIC DRIVE ELEMENT POSITIONED WITHIN SAID BASEBELOW SAID COVER, A MAGNETIC STIRRING ELEMENT POSITIONABLE WITHIN AVESSEL SUPPORTED ON SAID COVER, AND MEANS FOR ROTATING SAID MAGNETICDRIVE ELEMENT TO STIR THE CONTENTS OF SAID VESSEL BY ROTATING SAIDMAGNETIC STIRRING ELEMENTS, A TEMPERAFIELD LINKAGE BETWEEN SAID MAGNETICELEMENTS, A TEMPERATURE REGULATION DEVICE COMPRISING A THIN, FLATHOUSING OF NON-MAGNETIC MATERIAL, DEFINING A FLUID-TIGHT CHAMBER HAVINGAN EFFECTIVE SURFACE AREA APPROXIMATING THE SURFACE AREA OF SAID COVER,POSITIONABLE ON SAID COVER INTERMEDIATE SAID COVER AND SAID VESSEL, ANDMEANS, INCLUDING INLET AND OUTLET CONDUITS CONNECTED TO SAID CHAMBER,FOR CIRCULATING FLUID THROUGH SAID CHAMBER TO REGULATE THE TEMPERATUREOF THE CONTENTS OF SAID VESSEL.